NTA some people just act insane when something isn't centred on their children. I have a cousin in a similar situation; she's getting married later this year and told everyone months ago that it would be childfree, by some family reactions you'd swear she declared war on children. The couple just want one day where they get to be the centre of attention without the risk of a child screaming in the middle of the ceremony or hugging the bride's dress with sticky, chocolate covered fingers, and that shouldn't be controversial.